Pump



Sept. 26, 1961 w. N. THOMPSON PUMP 5 Sheets-Sheet 1 Filed Sept. 2, 1958 Sept. 26, 1961 w. N. THOMPSON PUMP Filed Sept. 2, 1958 5 Sheets-Sheet 2 Sept. 26, 1961 w. N. THOMPSON PUMP 5 SheetsSheet 3 Filed Sept. 2, 1958 Sept. 26, 1961 w. N. THOMPSON PUMP 5 Sheets-Sheet 4 Filed Sept. 2, 1958 Sgpt. 26, 1961 w. N. THOMPSON 3,001,481

PUMP

Filed Sept. 2, 1958 5 Sheets-Sheet 5 3,001,481 FUR [P Walter N. Thompson, Mont Vernon, NIL, assignor to Improved Machinery Inc., Nashua, N.H., a corporation of Maine Filed Sept. 2, 1955i, Ser. No. 758,311 9 Claims. (Cl. 103-126) This invention relates to rotaly piston pumps and more particularly to a pump especially adapted for pumping thick iiuid suspensions, for example, paper pulp stock at consistencies, say, of the order of to It is an object of the present invention to provide a practical pump especially useful for pumping at high pressures, if desired, fibrous suspensions of paper pulp or the like at consistencies as high as 20% or even higher. It is a particular feature of the invention that the pump provided thereby is not only less expensive to build than heretofore known rotary piston pumps suitable for pumping thick stock, but may at the same time be made stronger. Also, the pump of the present invention has less hydraulic lock than heretofore known rotary piston pumps, so that breakage is less likely. Further, since the rotor arrangement of the pump of the invention is preferably symmetrical, a pump of the invention may be operated in either direction as desired.

According to the present invention, the above recited objects and features are provided by novel rotors, preferably utilized in pairs on a housing having inlet and outlet ports with a pair of opposed concave surfaces therebetween. Such rotors in general have a circumferential series of upstanding vane elements, for example, four, with concave valley elements therebetween, and are driven synchronously for interacting rotation in opposite directions.

The vane elements of such a rotor pair perform in general two unrelated scaling functions, they must cooperate with the concave surface portions of the rotor chamber in closely spaced pumping relationship thereto to move fluid through the pump housing, and they must also cooperate with the elements of the other rotor of the pair to seal oif or otherwise control back flow of fluid in the region between the rotors. Furthermore, with pumps intended to pump fiber-liquid suspensions such as paper pulp, the interrelationships of the rotor elements are complicated by the necessity of utilizing a scraping action for cleaning, rather than a rolling action, in order to avoid jamming by fiber, such as paper pulp. Heretofore, rotary piston pumps have attempted to solve the sealing problem by utilizing common sealing elements, usually the tip of the rotor vanes, both along the rotor chamber surfaces and between the rotors. Although this approach was generally satisfactory from an operational standpoint, it resulted in complicated and expensive rotor construction, mostly because of the need to accurately machine the large rotor valleys, coupled with the necessity of building the preferred conical rotors in two pieces, which weakened them. More important, utilization of the vane tip as the principal sealing element made it impossible to compensate for the inevitable wear by building up the rotor tip, since there was no practical way to adjust rotor spacing to establish simultaneously the desired clearance between vane tip and housing and between vane tip and rotor valley.

In the rotor of the present invention, most of these problems are solved by utilizing separate elements to perform the two sealing functions. More specifically, the vane tip is utilized for pumping alone, and other elements, in particular, extended shoulder portions spaced radially inwardly from the vane tip at each edge of the vane adjacent the valleys between the vanes control the back flow. With such construction, not only can the tip- Patented Sept. 26, 1861 housing clearances be adjusted, either by utilizing vanes having radially adjustable tips or simply by building up the tip, as by welding, and remachining, without affecting the clearance between rotors, but also, expensive machining of the valleys is entirely eliminated, the only machined surfaces being the axially extending shoulder sealing surfaces and their edge adjacent the vane, as well as the vane tips. This makes possible for the first time in a conical pump the utilization of a one-piece cast rotor with a tremendous improvement in rotor strength.

It is a further object of the present invention to provide novel rotor shapes, especially double conical with a central cylindrical portion to provide increased efficiencyyet without rotor end jamming problems.

For the purpose of further explaining the above and further objects and features of the invention, reference is now made to the following detailed description of a preferred embodiment thereof, together with the accompanying drawings, wherein:

FIGS. 1 and 2 are, respectively, a cross-sectional side elevation and a cross-sectional end elevation of a rotary piston pump according to the present invention;

FIGS. 3 through 7 are a series of partly diagrammatic partial cross-sectional elevations progressively representing relative angular positions of a rotor pair;

FIG. 8 is an isometric sectional view of half a rotor of the pump of FIGS. 1 and 2;

FIGS. 9 through 11 are partial sectional views of the rotor of FIG. 8, taken, respectively, on the lines 9-9, 1til0, and 11-11 of FIG. 2;

FIG. 12 is an end view of the rotor of FIG. 8;

FIG. 13 is a modification showing in cross section an adjustable blade vane, and

FIGS. 14 and 15 illustrate rotor shapes modified from that of the rotor of FIGS. 1 through 13.

Referring to the drawings, and first to FIGS. 1 and 2, the pump housing is indicated generally at 1, such housing having an inlet port 2 and an outlet port 3. Positioned therebewteen are upper and lower opposed concave surfaces, respectively numbered 4 and 5, preferably of double conical form with the greatest. diameter in the center, defining a rotor chamber. The rotary pistons or rotors, upper rotor 6 and lower rotor 8, including their integral shafts 7 and 9, respectively, are mounted in housing 1 in suitable bearings for rotation within the rotor chamber adjacent concave surfaces 4 and 5, respectively, about spaced horizontal axes generally perpendicular to the path of flow through the pump, and are provided with suitable seals hereinafter more fully described. At one end of the housing shafts 7 and 9 are extended to receive the synchronizing drive gears 10 and 11, respectively, and one of said shafts, here lower shaft 9, is further extended for driving by any suitable means, :not shown.

The novel rotors of the present invention and their operation are best shown in FIG. 8 as well as in FIGS. 1, 2 and 9 through 12, the series of partial sectional views, FIGS. 3 and 7 showing a 45 degree segment of the 360 rotation of a pair of rotors, such 45 degree segment, in effect, being repeated eight times to make up the full cycle of rotation in a four vane configuration. Since the two rotors 6 and 8 preferably are identical, similar reference numerals are applied to each of them. While these rotors are susceptible of embodiment in various forms in accordance with the principles of the invention, particularly as to their number of vane elements, they are illustrated in the preferred quadruple form of double conical rotor.

As shown, each of said rotors includes a circumferential series of four vane elements generally designated 20, with concave valley elements 30 therebetween, such val ley elements, since they perform no sealing function, being left in as-cast condition. The vane elements include relatively thin, outwardly extending blade portions having a radially outwardly extending symmetrical tip portion 22 sloping downwardly from the center line of the rotor toward its ends in closely spaced relationship with the conical rotor chamber surfaces, such blades having generally angular concave sides 24 which may in the main be left in as-cast condition. The blade port-ions operate as the pumping elements of the pair of rotors, moving liquid along the outer annular volume of the rotor chamber between each rotor and its respective concave housing surfaces, as shown by the arrows in FIG. 1.

At the base of the blade portion of each of the vane elements are provided circumferentially extended vane shoulder portions, defined at their radially outermost edges by an axially extending projecting angular edge 26, preferably in a four vane pump, with an included angle of 45 degrees between each pair of edges 26, whether measured across the vane or the valley. Such angle will vary with rotors having different numbers of vanes, and in general will be equal to 180 degrees divided by the number of vane elements. The edge 26 is located outside of pitch line P and is formed at its side adjacent a valley as by an accurately machined concavely curved axially extending sealing shoulder surface 27. The side of edge 26 adjacent the blade portion is defined by another accurately machined surface 25, the function of which is to provide a sufiiciently acute angle, preferably about 70 degrees, of edge 26 for clearance of a coacting rotor element and to locate said edge in one dimension. The edge 26 is located in another dimension by sealing surface 27,. which surface extends across pitch line P and terminates in an edge 28 which is spaced radially outwardly from the concave valley element 39. This necessarily results in a structure wherein the inner shoulder edges 28 are located closer to the radially extending vane center line than are the outer shoulder edges 26, since such edges, if without overlap, are spaced along a common radius line of the rotor. The concave sealing surface 27 is generated by the edge 26 of the mating rotor as it sweeps through the sealing engagement. The radial extent or length of sealing surface 27 is that generated surface of one rotor progressively traversed for sealing by the edge 26 of the other rotor measured radially of the first rotor in terms of linear dimension from the first rotor center and extending between edges 26 and 28 thereof, both rotors being identical in the preferred embodiment. In terms of degrees of rotation of the rotor the sealing surface 27 is at laest 45' degrees, in general at least 180 degrees divided by the number of vane elements, and preferably somewhat greater, to provide an overlap of about 5 degrees of rotor rotation between adjacent sealing surfaces. The location of the pitch line P is, from a theoretical standpoint, in the center of seating surface 27, that is, assuming for the moment a sealing surface without overlap in a four-vane pump, edges 26 and 28. would both be located along common radius lines 22.5 degrees of rotor rotation on each side of the pitch line P. The overlap is preferably provided on surface 27 radially outwardly of the pitch line, so that edge 26 is located 5 degrees of rotor rotation outwardlyfrom its theoretical position, or 27.5 degrees of rotor rotation from pitch line P which spaces the outer edge 26 even further away from the radially extending vane center line.

With the rotor structure of the present invention, it is the shoulder portions which accomplish the inter-rotor sealing, with at least one sealing shoulder surface 27 of one rotor of the pair cooperating with at least one projecting angular edge 26 to provide positive control of back flow of fluid in the region between the rotors throughout their complete rotation. The valley element 30 is spaced generally radially inwardly of and between I the inner edges 28 of sealing shoulder surfaces so that there is substantial clearance for free flow of liquid between a blade tip portion 22, and the surface of a valley element 30.

It should'be noted particularly that the vanes 20 of the present invention are preferably made symmetrical about their radial center lines for ambidirectional pumping, yet without jamming problems even when pump-ing fibrous material such as thick stock. To that end, the blade tip portions 22 may have a conical surface of about 2 degrees peripheral length, providing suitable strength with sharp edges. Such tips, too, may be extended as by welding and remachining to compensate for housing wear without afiecting the scaling function of the pump. Also, if desired, removable or radially adjustable vane tips may be provided as shown in FIG. 13 wherein a vane tip is provided with a separate knife blade 40' recessed therein, said blade 40 having a slot 41 therein and shims 42 for adjustment, a bolt 43 being provided for maintaining said blade in position. Likewise, too, the shoulder elements may be repaired by welding and remachining for correct clearance between the rotor elements themselves.

Preferably, the rotors according to the present invention are of double conical form, as shown, with the greatest tip diameter in the center of the rotor and with the tips sloping downwardly toward the end of the rotor. At the same time, the valley elements 31'; slope upwardly from their greatest depth at the center of the rotor to their least depth at the end of the rotor, such valleys nevertheless throughout their area maintaining substantial spacing from a rotor tip. The shoulder sealing surfaces 27' and their edges 26 and 2% extend axially so that said surfaces are of substantially constant width, with edges 26 and 28 being straight lines throughout the entire length of the rotor in spite of its double conical configuration. At the end of a rotor, the width of the sealing surface 27, in general, determines the inward radial spacing of valley element 30 relative to edge 26, and in fact valley 30 may even be slightly outwardly thereof, as seen in FIG. 12, since vane tip clearance is not there a problem.

The operation of rotors in sealing against blackflow between rotors is best shown in FIGS. 3 through 7. The pumping operation of the vanes 20 in cooperation with their surrounding housing, as shown in FIG. 1, is generally conventional and need not herein be described in detail, except to point out that it is entirely eifective for pumping thick stock up to about 20 percent consistency and at high pressures, if desired. Clearances between vane tips and housings, in a pump having a conical rotor diameter of 10 to 15 inches may be about 0.015 to 0.030 inch, with the overall length of the rotor being about 15 inches.

Referring now to FIGS. 3 through 7, a complete 45 degree segment showing a sealing cycle of one shoulder element with another and transfer of the sealing function to the next succeeding pair of shoulder elements in five 9 degree steps, throughout the length or radial extent of shoulder surface 27 expressed in degrees of notation of the rotors, such cycle being repeated eight times each revolution of the synchronously rotated rotors.

In FIG. 3, the sealing edge 26 of bottom rotor 8 has just come into sealing relationship with the sealing sur face 27 of the top rotor 6. In FIGS. 4 and 5, as the tip 22 passes freely across the shoulder elements on the other side of valley element 30 of lower rotor 8, the sealing edge 26 of upper rotor 6 comes into contact with the innermost extent of the sealing surface 27 on lower rotor 8, the sealing edge of said lower rotor simultaneously moving away from the sealing surface of the upper rotor so that a closed compartment is not formed between the opposed sealing surfaces of the rotors. In FIG. 6, the sealing edge 26 of upper rotor 6 continues to advance almost in a radialdirection progressively along the entire length or radial extent of opposed sealing surface 27 of lower rotor 8 between its edges, until, in FIG. 7, it has advanced almost to the end with tip 22 positioned centrally in valley element 30 but well clear of the surface thereof and with the shoulder elements on the opposite side of said valley element just come into engagement. It will also be noted in FIG. 7 that there is a small degree of overlap, preferably about 5 degrees, whereby both shoulder elements on each side of the vane or upper rotor 6 are engaged with both shoulder elements on each side of the valley of lower rotor 8. This has been found to be advantageous, and is not harmful both because the volumetric change during such overlap is only about 1.5 percent maximum at the center, and because of the open clearance between a vane tip and valley. Preferably the clearance between a sealing edge and its cooperating sealing surface with rotors of the general dimensions set forth above is about 0.015 to 0.030.

In order to provide suitable rotor shaft sealing according to the present invention, the shafts are of smaller diameter than the minimum rotor end diameter, providing a vertical end face 50 at each end of a rotor. The housing is provided in its shaft receiving bores with a lantern ring 52 of H shaped configuration, such ring being supplied with purging water of pressures 5 to 10 pounds greater than the maximum pump discharge pressures through a suitable inlet channel 53 and reservoir 54. Preferably a discharge channel is also provided for continuous flow of water through the lantern ring. In order to keep stock dilution to a minimum, the clearance between the lantern ring 52 and a shaft are preferably about 0.005 inch. The lantern ring is preferably of a dissimilar material than the shaft to prevent galling, for example, it may be of a lead-tin alloy, the rotor and shaft being of stainless steel.

FIGS. 14 and 15, respectively, show modified rotor shapes, respectively, cylindrical throughout its length and generally designated 60, and double conical at its ends with a cylindrical central portion, generally designated 70. As may be seen from FIG. 14, a cylindrical rotor 60, wherein the valley 62 is a straight line, provides high efiiciency in terms of rotor length and is entirely suitable for pumping substances wherein jamming is not a problem. However, in pumping fibrous suspensions such as paper pulp, there is at least a tendency to jam fibers be tween the generally radially extending edges of the valley 62 of a cylindrical rotor. However, by raising the bottom of a valley 30 or 72 adjacent the ends to nearly meet the vane tip except for the intervening sealing surface, jamming problems are eliminated. This need not be done throughout the length of the rotor, but rather only on its end portions as shown in FIG. 15, with a cylindrical central portion providing a greatly increased pumping efficiency over rotors of strict double conical form. Furthermore, as explained above, the rotor sealing surfaces being parallel to the rotor axis irrespective of external rotor shapes, such novel rotor shapes as is shown in FIG. 15 may be readily manufactured, as may rotor shapes having curved surfaces of revolution if such be desired for any reason.

The present invention is a continuation-in-part of my earlier application Ser. No. 747,207, filed July 8, 1958, now abandoned, and provides, then, by utilization of a novel principle wherein separate elements than the pumping vanes are provided for inter-rotor sealing in a rotary piston pump, a novel pump rotor element operable preferably in pairs in a housing for pumping of difficult liquid suspensions such as thick fibrous paper pulp stock at consistencies as high as percent. Various modifications of the invention within the spirit thereof and the scope of the appended claims will be apparent to those skilled in this art.

I claim:

1. A rotary piston pump comprising a housing having end walls and a pair of opposed concave surface portions of circular cross section extending between said end walls defining a rotor chamber with inlet and outlet ports in opposite walls of said housing between said circular surface portions, a pair of like interacting rotors mounted in said chamber for rotation about spaced parallel axes parallel to the circular surface portionsof said chamber, and means for synchronously driving said rotors for interacting rotation in opposite directions, each of said ro tors'having a circumferential series of upstanding vane elements with concave valley elements therebetween, said vane elements includingvane blade portions with a tip portion cooperating with said circular surface portions of said rotor chamber in closely spaced pumping relationship thereto to pump fluid through said housing and extended vane shoulder portions at each side of a blade portion adjacent a valley element and spacing said tip portion from said valley element for controlling back flow of fluid in the region between said rotors by moperation with the shoulder portion of the interacting rotor of said pair, said shoulder portions each comprising a concavely curved axially extending sealing shoulder surface terminating at its radially outer side in an axially extending projecting angular edge adjacent. said vane blade portion and at its inner side terminating in an inner edge at said valley element with said outer side edge spaced radially outwardly with respect to said inner side edge and with said inner side edges on opposite. sides of a vane element located closer to the center line of said vane element than are said outer side edges, and having an angular extent in terms of degrees of rotation of said rotors of more than degrees divided by the number of said vane elements, said valley elements being spaced radially inwardly for substantial clearance between a blade tip portion and said valley element throughout the entire extent of said valley element, with at least one vane shoulder portion of one rotor cooperating with one vane shoulder portion of the other rotor with said projecting angular edge of said other rotor advancing progressively along said shoulder surface in sealing relationship therewith from one edge to the other edge thereof to provide a scraping action for cleaning without jamming with substantial control of back flow in the region between said rotors throughout complete rotation of said rotors.

2. A pump as claimed in claim 1 wherein said projecting edge of said other rotor advances along said shoulder substantially in a radial direction inwardly toward the center of said one rotor from the shoulder edge to the valley edge thereof on the discharge side of said pump.

3. A pump as claimed in claim 1 wherein each of said rotors has a cylindrical central portion and inwardly sloping conical end portions providing a reduced diameter end.

4. A pump as claimed in claim 1, wherein the sealing shoulder surface outer and inner edges of each said rotor are on opposite sides of the pitch line of said rotor and said shoulder surface extends in a smooth curve generally perpendicular to and across said pitch line.

5. A pump as claimed in claim 4 wherein said outer and inner edges of a shoulder surface are located generally along a common radius line.

6. A pump as claimed in claim 5 wherein said shoulder surface is extended at its outer edge to provide an overlap of about 5 degrees between adjacent sealing shoulder surfaces.

7. A rotary piston pump comprising a housing having end walls and a pair of opposed concave surface portions of circular cross section extending between said end walls defining a rotor chamber with inlet and outlet ports in opposite walls of said housing between said concave surface portions, a pair of like interacting rotors mounted in said chamber for rotation about spaced parallel axes parallel to the circular surface portions of said chamber, and means for synchronously driving said rotors for interacting rotation in opposite directions, each of said rotors having a circumferential series of upstanding vane elements with concave valley elements therebetween, said vane elements including vane blade portions with concave sides and a tip portion cooperating with said circular surface portions of said rotor chamber in closely spaced pumping relationship thereto to pump fluid through said housing and vane shoulder portions at each side of a blade portion adjacent a valley element for controlling back flow of fluid in the region between said rotors by cooperation with the shoulder portion of the interacting rotor of said pair, said shoulder portions each comprising a concavely curved axially extending sealing shoulder surface terminating at its radially outer side in an axially extending projecting angular edge adjacent said vane blade portion and at its inner side terminating in an inner edge at said valley element, and with said outer side edge spaced radially outwardly with respect to said inner side edge and with said inner side edges on opposite sides of a vane element located closer to the center line of said vane element than are said outer side edges, and having an angular extent in terms of degrees of rotation of said rotors of more than 180 degrees divided by the number of said vane elements, said valley element being spaced radially inwardly between adjacent sealing shoulder surfaces for substantial clearance between a blade tip portion and said valley element throughout the entire extent of said valley element, with at least one said shoulder surface of one rotor of said pair cooperating with at least one said projecting angular edge of the other rotor of said pair with said projecting angular edge of said other rotor advancing progressively along said shoulder surface in sealing relationship therewith from one edge to the other edge thereof to provide a scraping action for cleaning without jamming with substantial control of back flow of fluid in the region between said rotors throughout complete rotation of said rotors.

8. A rotary piston pump comprising a housing having end walls and a pair of opposed concave conical surface portions extending between said end walls defining a rotor chamber with inlet and outlet ports in opposite Walls of said housing between said conical surface portions, a pair of like unitary cast metal interacting rotors mounted in said chamber for rotation about spaced axes parallel to the axes of the conical surface portions of said chamber, and means for synchronously driving said rotors for interacting rotation in opposite directions, each of said rotors having a circumferential series of upstanding vane elements With concave valley elements therebetween, said vane elements including vane blade portions with concave sides and a tip portion cooperating with one of said conica-l surface portions of said rotor chamber in closely spaced pumping relationship thereto to pump fluid through said housing and vane shoulder portions at each side of a blade portion adjacent a valley element and spacing said tip portion from said valley element for controlling back flow of fluid in the region between said rotors by cooperation with the shoulder portion of the interacting rotor of said pair, said shoulder portions each comprising a concavely curved axially extending sealing shoulder surface terminating at its radially outer side in an axially extending projecting angular edge adjacent said vane blade portion and at its inner side terminating in an inner edge at said valley element, with said outer side edge spaced radially outwardly with respect to said inner side edge and with said inner side edges on opposite sides of a vane element located closer to the center line of said vane element than are said outer side edges, and having an angular extent in terms of degrees of rotation of said rotors of more than degrees divided by the number of said vane elements to provide an overlap of about five degrees of rotor rotation between adjacent sealing shoulder surfaces, said valley element sloping upwardly and being spaced radially inwardly between adjacent sealing shoulder surfaces for substantial clearance between a blade tip portion and said valley element throughout the entire extent of said valley element, with said tip portion and said valley element being radially spaced from one another by said shoulder surface adjacent the end of said rotors, with at least one said shoulder surface of one rotor of said pair cooperating with at least one said projecting angular edge of the other rotor of said pair with said projecting angular edge of said other rotor advancing progressively along said shoulder surface in sealing relationship therewith from one edge to the other edge thereof to provide a scraping action for cleaning without jamming with substantial control of back flow of fluid in the region between said rotors throughout complete rotation of said rotors.

9. A pump as claimed in claim 8 wherein said vane blades have radially adjustable tips.

References Cited in the file of this patent UNITED STATES PATENTS 12,350 Holly Feb. 6, 1855 533,293 Green Jan. 29, 1895 924,773 Hanman June 15, 1909 1,252,160 Pagel Jan. 1, 1918 1,287,268 Edwards Dec. 10, 1918 1,348,773 Auger Aug. 3, 1920 1,369,073 Auger Feb. 22, 1921 1,756,977 Enlind May 6, 1930 2,195,886 Hawley Apr. 2, 1940 2,439,427 Guibert et al. Apr. 13, 1948 2,460,278 Cook Feb. 1, 1949 FOREIGN PATENTS 773,646 France Sept. 3, 1934 

